1. Field of the Invention
The present invention relates to methods for removing halogen-containing residues from a substrate.
2. Description of the Prior Art
Ultra-large-scale integrated (ULSI) circuits may include more than one million electronic devices that are formed on a semiconductor substrate, such as a silicon substrate, and cooperate to perform various functions within the devices. Typically, the transistors used in the ULSI circuits are complementary metal-oxide-semiconductor (CMOS) field effect transistors. A CMOS transistor has a gate structure including a polysilicon gate electrode and gate dielectric, and is disposed between a source region and drain regions that are formed in the substrate. Such formation of integrated circuits involves sequentially forming or depositing multiple electrically conductive and insulative layers in or on the substrate. Etching processes may be used to form geometric patterns in the layers or vias for electrical contact between the layers. General etching processes include wet etching, in which one or more chemical reagents are brought into direct contact with the substrate, and dry etching, such as plasma etching.
Plasma etching is commonly used in the fabrication of transistors and other electronic devices. During plasma etching processes used to form transistor structures, one or more layers of a film stack (e.g., layers of silicon, polysilicon, hafnium dioxide (HfO2), silicon dioxide (SiO2), metal materials, and the like) are typically exposed to etchants including at least one halogen-containing gas, such as hydrogen bromide (HBr), chlorine (Cl2), carbon tetrafluoride (CF4), and the like. Such processes induce halogen-containing residues to build up on the surfaces of the etched features, etch masks, and elsewhere on the substrate.
When exposed to a non-vacuumed environment (e.g., within factory interfaces or substrate storage cassettes) and/or during consecutive processing, gaseous halogens and halogen-based reactants (e.g., bromine (Br2), chlorine (Cl2), hydrogen chloride (HCl), and the like) may be released from the halogen-containing residues deposited during etching. The released halogens and halogen-based reactants create particle contamination and cause corrosion of the interior of the processing systems and factory interfaces, as well as corrosion of exposed portions of metallic layers on the substrate. Cleaning of the processing systems and factory interfaces and replacement of the corroded parts is a time consuming and expensive procedure. In addition to corroding the factory interface over time, the volatile chemicals outgassing from untreated wafers will damage the photoresist on unetched wafers in the FOUP. Corrosion to the factory interface is a long term problem, however, the damage to unetched wafers is immediate
Therefore, methods for removing the halogen-containing residues after the etching process are needed. Moreover, the efficiency of the removal process is also important so as not to reduce the manufacturing throughput.